Nonlinear Self-excited Vibration Analysis Of Rotor System

With the development of science technology and the application of ultra-supercritical units, people are pay more and more attention to the rotor system problem due to self-excited vibration. Studying of self-excited vibration excitation source, which including alford force, seal force, oil film force, has important practical significance to the stability and security of unit operation. Self-excited vibration of the rotor has a strong nonlinearity. Vibration characteristics of the rotor are complex. It is difficult to solve vibration problem.Dynamics theory also provide support for this study. However, most studies are limited to self-excited vibration excitation force model, and relatively few studies consider the effect of coupling excitation source, and relatively few studies consider the vibration characteristics of the high-speed rotor system supported by gas bearing.In this paper, the object is rotor system. The author use a numerical method and Matlab software to study the vibration response in excitation force. The nonlinear vibration characteristics in a single self-excited vibration excitation force are studied, and the nonlinear vibration characteristics in three coupling exciting force are also studied. Nonlinear vibration characteristics is studied in single excitation force by contrast with coupling three exciting force. The author use a experimental method and Dasp software to study on-line monitoring and suppression measures of the self-excited vibration. The main research work are as follows:(1) The basic theory of nonlinear rotor dynamics and research methods of nonlinear differential equations are introduced briefly. And three kinds of self-excited vibration excitation force model are introduced.(2) Three exciting force, which acting on rotor system model, are established alone. Vibration response is calculated by the Runge-Kutta method. Vibration characteristics at different speeds are analyzed. Meanwhile, When alford force acting on rotor system model alone, the relationship between relative intake rate and cross equivalent stiffness which generated by alford force are studied. The increase of the intake rate cause the rapid increase of cross equivalent stiffness, even can cause system instability. When sealing force acting on rotor system model alone, seal pressure and seal gap are studied. Reasonable seal pressure and seal gap can help to control the movement behavior of the rotor. When oil film force acting on rotor system model alone, film viscosity studied. When the oil film viscosity decrease, rotor system is postponed into chaotic motion.(3) Three coupling exciting force acting on rotor system model, are established. Vibration response of the model is calculated by the Runge-Kutta method. Nonlinear vibration characteristics is studied in single excitation force by contrast with coupling three exciting force.(4) On-line monitoring and suppression measures of the self-excited vibration are conducted on rotor system, which is supported by gas bearing. Experimental researches are conducted on the test bench. Different tests about the on-line monitoring of the rotor vibration characteristics are conducted, which are used different bearing gas pressures. Different tests about the rotor vibration characteristics are conducted, whether are added damping pads between the stand and the test bench.Results of this study can provide some theoretical basis about the instability mechanism of self-excited vibration in steam turbines and other rotating machineries, and can also provide some test basis for the on-line monitoring and vibration suppression of rotor system.